1. Field of the Invention
The present invention relates to an infrared wide-angle single lens for use in an infrared optical system, which is employed in a non-contact type temperature measuring device serving primarily for detection of temperature conditions in a room and the like.
2. Description of the Prior Art
In a conventional non-contact type temperature measuring device, there has been used an inexpensive single-element infrared-ray detector. In such an infrared detector, a thermal image of infrared rays is formed on an infrared detector through an infrared optical system having a narrow angle of view. Therefore, when a temperature is measured over a wide range of a thermal object, a scanning operation is effected to measure temperatures of individual ranges. However, such infrared detectors have been so complicated in construction in all cases that it is difficult to reduce the size and price of the device, disadvantageously.
With the arrangement of the infrared detector as mentioned above, the detector is be set with a problem that two-dimensional scanning is necessitated, which leads to difficulties in reducing the size and price of the device.
In recent years, research and studies have been conducted upon inexpensive arrayed or two-dimensional infrared detectors. As a result, there is a desire to make an infrared wide-angle lens for use in an infrared optical system capable of forming an image of an object in a wide range at a time on the detector and yet capable of making the system small in size and low in price.